This invention relates to a detonator assembly.
An electronic detonator holds advantages, over other detonator types, in that, inter alia, it allows for flexibility in programming of the operation of the detonator and, in particular, the detonator is capable of executing accurately a timing interval, even of millisecond duration.
Normally use is made of electrical conductors, e.g. in a two-wire or four-wire configuration, to interconnect a plurality of electronic detonators thereby to establish a blasting system. The cost of the electrical conductors, typically made from copper, can be relatively high and, at least for this reason, increasing attention has been paid to interconnecting electronic detonators using signal tubes (also referred to as “shock tubes”) in order to make up a blasting system.
A shock tube is robust and relatively inexpensive and possesses a number of advantages over electrical conductors. In a blasting system which is based on the use of a number of electronic detonators interconnected by means of shock tubes, an electrically conductive path is however not established between the detonators and an external device such as a blasting machine or tagger. Each detonator must be capable of withstanding the effects of pressure produced when adjacent detonators ignite respective explosive charges. For this reason a detonator housing is normally made from a metal such as aluminium or copper. Unfortunately the metallic housing is, inherently, electrically conductive and acts as an electromagnetic shield. This feature makes it difficult, in a shock tube-based system, to establish reliable communication links between a communication circuit inside a detonator housing and an external device.
A need exists for a means of establishing communication between an external device and a communication circuit inside a detonator housing without making an electrically conductive connection between the external device and the communication circuit.